The relationships of catecholamines and the diurnal patterns of spontaneous uterine activity and of experimental alterations of uterine environment upon uteroplacental circulation will be evaluated. Chronically implanted sensors will monitor intrauterine pressure, uterine blood flows, arterial and venous blood pressures, cardiac output, and body temperature. Electronic integration of measured parameters will facilitate evaluation of the effect of stimuli on myometrial activity in both pregnant and nonpregnant monkeys in an effort to elucidate some of the factors involved in the physiology and control of myometrial contractility and the onset of labor. Radioisotopes and other indicators will be used to analyze various aspects of placental and nonplacental uterine blood flow. A primate colony will be maintained.